Reading serial on Linux USB from mkr wifi 1010

Hi folks -

I’m trying to get serial reading working from my desktop. I’m programming a Mkr WiFi 1010 with a trivial hello world program:

void setup() {
   pinMode(LED_BUILTIN, OUTPUT);
   Serial.begin(9600);
}

void blink(int onOffTime) {
   Serial.println("Blink on");
   digitalWrite(LED_BUILTIN, HIGH);
   delay(onOffTime);
   Serial.println("Blink off");
   digitalWrite(LED_BUILTIN, LOW);
   delay(onOffTime);
}

void loop() {
   blink(150);
   blink(150);
   blink(150);
   blink(150);
   blink(150);
   delay(1000);
}

My host computer is a Linux box, and I’m using arduino-cli to program the Mkr Wifi 1010. I program it like this:

arduino-cli upload -p /dev/ttyACM1 MyBlink

I can tell that the programming is working because it does my fancy blink pattern on the unit.

I’m trying to read from the serial port to see the “Blink on” and “Blink off” messages, and am not able to get anything out. Here’s how I’m trying to do it:

% arduino-cli board list
Port         Type              Board Name            FQBN                     Core
/dev/ttyACM0 Serial Port (USB) Unknown
/dev/ttyACM1 Serial Port (USB) Arduino MKR WiFi 1010 arduino:samd:mkrwifi1010 arduino:samd
/dev/ttyS0   Serial Port       Unknown

% stty -F /dev/ttyACM1 -a
speed 9600 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc

% tail -f /dev/ttyACM1

The last line never outputs anything.

Any ideas what I’m doing wrong or other things to try?

Interesting! I don't know why tail -f doesn't work, but this did:

screen /dev/ttyACM1 9600